Brain content

Although apoE HDL particles are formed by astrocytes in vitro, the brain contents of apoE knockout (-/-) were not found to differ in lipid content in comparison to those obtained from normal animals [14]. A probable explanation is that newly synthesized cholesterol can be transported from astrocyte ER to plasma membrane via an alternative route that employs caveolae to form apoAl-HDL [15]. 

The amino acid L-tryptophan is the precursor for the synthesis of 5-HT. The synthesis and primary metabolic pathways of 5-HT are shown in Figure 13-5. The initial step in the synthesis of serotonin is the facilitated transport of the amino acid L-tryptophan from blood into brain. The primary source of tryptophan is dietary protein. Other neutral amino acids, such as phenylalanine, leucine and methionine, are transported by the same carrier into the brain. Therefore, the entry of tryptophan into brain is not only related to its concentration in blood but is also a function of its concentration in relation to the concentrations of other neutral amino acids. Consequently, lowering the dietary intake of tryptophan while raising the intake of the amino acids with which it competes for transport into brain lowers the content of 5-HT in brain and changes certain behaviors associated with 5-HT function. This strategy for lowering the brain content of 5-HT has been used clinically to evaluate the importance of brain 5-HT in the mechanism of action of psychotherapeutic drugs. 

Kanada M, Miyagawa M, Sato M, et al. 1994. Neurochemical profile of effects of 28 neurotoxic chemicals on the central nervous system in rats (1) effects of oral administration on brain contents of biogenic amines and metabolites, hid Health 32 145-164. 

Verbalis JG, Gullans SR. Hyponatremia causes large sustained reductions in brain content of multiple organic osmolytes in rats. Brain Res 1991 567 274-282. 

Mass effect—An increase in intracranial pressure due to a space-occupying lesion in the brain, usually leading to a shift in brain contents, evident by imaging techniques. 

Perry, T.L., Krieger, C., Hansen, S. and Tabatabaei, A. (1991). Amyotrophic lateral sclerosis fasting plasma levels of cysteine and inorganic sulfate are normal, as are brain contents of cysteine. Neurology 41 487-490. 

Its meehanism of aetion may be related to inereased brain levels of the inhibitory neurotransmitter Gamma-aminobutyric acid (GABA). This increase in brain content of GABA is probably due to the inhibition by valproate sodium of the enzymes that metabolize GABA. 

FIGURE 17.1 Effects of cisplatin exposure on shrew brain contents of 2-AG and anandamide. Different groups of shrews (Cryptotis parva) were injected with varying doses of cisplatin (0, 5,10, and 20 mg/kg, i.p., n = 4 per group) and 30 min later, the animals were sacrificed by rapid decapitation, and whole brains were frozen at -80°C until endocannabinoid analysis. Significantly different from corresponding vehicle-treated control group. 

Butterworth RF, Tonon MC, Desy L, Giguere JF, Vaudry H, Pelletier G. Increased brain content of the endogenous benzodiazepine receptor ligand octadecemeuropeptide (ODN) following portacaval anastomosis in the rat. Peptides, 12, 119-125, 1991... 

A sensitive and specific radioimmunoassay for TRH has established that the hypothalamus contained only 31.2% of the total brain content of TRH and that appreciable amounts of the hormone were found in all areas of the brain except the cerebellum [170-171]. 

Investigations in recent years have indicated a possible relationship between brain amine metabolism and Parkinson s disease. Dopamine, noradrenaline, and serotonin have a characteristic distribution in the human brain. Dopamine is found in especially high concentration in the nuclei of the neostriatum, i.e. in the caudate nucleus and putamen noradrenaline and serotonin predominantly in the hypothalamus, in the central grey matter, and in the reticular formation. The brain content of these amines is reduced in patients... 

The enzyme L-aromatic amino acid decarboxylase (AADC, EC 4.1.1.28) lacks substrate specificity and has been considered to be involved in the formation of the catecholamines and serotonin. There are many differences in the optimal conditions for enzyme activity, including kinetics, affinity for PLP, activation and inhibition by specific chemicals, and regional differences in the distribution of DOPA and 5-HTP decarboxylation activities. Nonparallel changes in brain monoamines in the vitamin Bg-deficient rat have been reported (7-9). Brain content of dopamine and norepinephrine were not decreased during deficiency, whereas serotonin was significantly decreased. 

Meso-2,3-dimercaptosuccinic acid (DMSA) is knovm to be effective in decreasing body burden and brain content of Hg in experimental animeds. This compound has also been found to be much less toxic than agents such as BAL (British anti-Lewisite) or penicillamine. 

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